On Thu, Nov 18, 2021 at 4:50 PM Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > On Thu, Nov 18, 2021 at 03:51:38PM +0100, Bartosz Golaszewski wrote: > > This is another shot at the gpio-sim testing module. As there was no > > reasoning with configfs maintainers for many months, this time the whole > > concept of committable items has been dropped. Instead, each configfs > > chip item (or rather a group - more on that later) exposes a new > > attribute called 'live'. Writing 1 to it brings the chip on-line > > (registers the platform device) and writing 0 tears it down. > > > > There are some caveats to that approach - for example: we can't block > > the user-space from deleting chip items when chips are live but is just > > handled by silently destroying the chip device in the background. > > > > Andy (rightfully) pointed out that parsing of the lists of line names is > > awkward so in this iteration it's been replaced by a system that is more > > elegant and will allow to easily extend configuration options for > > specific GPIO lines. This is achieved by turning the chip's configfs > > item into a configfs group and allowing the user-space to create > > additional items inside it. The items must be called line<offset> (e.g. > > line0, line12 etc.) where the offset part indicates to the module the > > offset for which given item stores the configuration for. Within each > > such line item, there are additional attributes that allow specifying > > configuration for specific lines. Currently we only support the 'name' > > attribute but I plan to extend that to support GPIO hogging too. > > One question here. Since you know how the driver looks like in both cases > (with and without committable items), would it be possible to modify what > you proposed here to the former one in case ConfigFS gains the feature? > This would completely change the user interface unfortunately. We could extend it but we would need to keep this one too most likely. TBH I don't see the committable items merged anytime soon, and this is GoodEnough®. Bart
